This invention relates to the field of vacuum thermoforming and in particular relates to materials and processes for providing a finished product having a fabric-like surface as well as the thermoformed articles employing such materials.
Vacuum thermoforming has perhaps found its greatest application in the field of packaging wherein items have been protected by closely fitting packaging which conforms to the shape of even irregular items. In some such processes, often referred to as "skin packaging", the item is placed on a cardboard backing. A thermoplastic material such as a film of polyester, polyvinylidene chloride, Polyvinyl chloride, polyvinyl acetate, polyethylene or polypropylene is laid over the item and is heated and then drawn down onto the item using vacuum. The film, owing to its thermal plasticity, will conform to the shape of the item and, in the plastic state, will adhere to the cardboard backing and remain so adhered after cooling, thus encapsulating the item between the film and the backing. In the so-called "blister packaging" application, the film is heated and vacuum formed by being drawn into a mold designed to produce a film shaped to accommodate the item to be packaged. The item is then placed into the so-shaped film, often while still in the mold, and a cardboard backing is then adhered to encapsulate the item.
It has been discovered that a particularly useful application of vacuum thermoforming is in the field of liners such as hoodliners, trunkliners, and roof liners (i.e., headliners) for inner surfaces of vehicles . These liners comprise a relatively thick body of noise and/or heat insulating material such as, for example, fiberglass. The body is molded to fit the contours of the inner surface of automobile hoods, trunks and roofs and as such, the body comprises an irregular shape whose surfaces are interrupted by protrusions and depressions.
While the fiberglass body provides excellent insulation properties, both for aesthetic and practical purposes, the nature of this material presents drawbacks. Firstly, the fiberglass insulation tends to be brittle, causing breaking of fiber and formation of particles which are disadvantageous both during the liner installation process and in use. Secondly, the surface tends to be rough and aesthetically displeasing.
Accordingly, there have been several suggestions for applying to this insulation surface a material which Protects against such breakage and is more aesthetically Pleasing. Such suggestions are to be found, for example, in A. Marzocchi et al. U.S. Pat. No. 3,263,530 wherein a fiberglass headliner is provided with a laminate cover comprising layers of thermoplastic film sandwiching a glass fiber cloth and adhered by means of heat and compression. Further, in U.S. Pat. No. 4,002,367 there is described a nonwoven cover adhered to the fiberglass body of a liner by employing an adhesive. Further still in Harmes U.S. Pat. No. 3,620,906 wherein a polyethylene layer and a fiber layer are laminated to the fiberglass body.
While each of these suggestions have to an extent, improved the installation and use problems associated with the fiberglass insulation liners, they each suffer from drawbacks. In some instances the prior suggestions result in a plastic like outer surface which is visible in the finished vehicle and aesthetically displeasing. In other instances, the prior suggestions result in a requirement for the installer to handle several different layers of material and, in certain circumstances, handle relatively weak, easily torn, easily creased, nonwoven materials.
Accordingly, there is a need for a material which can be combined with an insulating body such as a fiberglass body, which can have an irregular surface, which can be handled and installed without extraordinary Care, and which will present an aesthetically pleasing surface.